How Quantum Computing Threatens Blockchain

Idalia Friedson

There has been a lot of hype concerning Bitcoin and cryptocurrencies of late. But it is blockchain, the electronic architecture on which cryptocurrencies run, that is the truly revolutionary technology.

Blockchain is a decentralized accounting system that verifies records through a shared ledger of transactions. Each computer in the network hosts a copy of the ledger, and when a transaction is completed, it is verified against the ledger stored on all the other network computers. If all the ledgers match, then that transaction is encrypted with others into what’s known as a block. The new block is then added to existing blocks to form a chain of blocks, or a blockchain.

The potential uses of blockchain extend far beyond cryptocurrencies. They include securing electronic heath records, creating smart contracts, and electronic voting. Blockchain is even being touted as the potential solution to the Department of Defense’s (DoD) logistics challenges—from DoD’s perspective, the consensus structure of blockchain mitigates the security risks of a single point of failure and allows for inventory suppliers both large and small to track their shipments. And in December, President Trump signed a bill calling for exploration into the potential benefits of blockchain for the federal government.

The dirty little secret, though, is that the technology could be rendered useless by a quantumcomputer hack.

Quantum computers, currently in development, will be more powerful than today’s classical computers because they are driven by quantum physics. Rather than using a binary system of bits, where each bit is 1 or 0, quantum computers use quantum bits or “qubits” composed of physical particles, often single photons. Because a bit is only ever 1 or 0, a classical computer calculates in a linear fashion. In contrast, the quantum physical properties of superposition and entanglement mean a qubit is both 1 and 0 at the same time, which allows for exponentially greater computing power.

At the same time, quantum computers pose a major threat to the asymmetric encryption system used to secure most electronic data, including blockchain. This system relies on math problems that take too long for a classical computer to solve. The only way to crack this encryption is to reverse factor a large semi-prime number to its original primes. Such a calculation takes eons for a classical computer, but will be instantaneous for a large universal quantum computer—even against blockchain. Charles Harvey Jr., senior adviser for American Defense International, has said, “I call the day quantum computers are able to break classic computer encryption methods ‘Q-Day.’ Q-Day is coming.”

But if a quantum computer poses a threat to blockchain as it exists now, quantum cybersecurity promises a solution. In fact, incorporating emerging quantum cybersecurity in three stages can save blockchain from the fate of other systems made obsolete by new technologies.

The first and most immediate solution is to strengthen existing encryption algorithms by adding in truly random numbers, or so-called quantum keys, which are the world’s strongest encryption keys. True randomness can only be found in nature, which is why scientists measure the crackle of energy in the fabric of the universe as it spontaneously creates and self-destructs. Quantum physicists harness this crackling quantum noise and convert it into true random numbers.

Quantum random-number generators are already being implemented today by banks, governments, and private cloud carriers. Adding quantum keys to blockchain software, and all encrypted data, will provide added security against both a classical computer and a quantum computer.

The next step is to develop quantum-resistant algorithms. The National Institute of Standards and Technology, part of the U.S. Department of Commerce, is currently reviewing submissions for these next-generation algorithms. Just as asymmetric encryption uses difficult math problems to stump classical computers, quantum-resistant algorithms will use difficult math problems to stump a quantum computer. The challenge lies in creating useful math problems that actually can stump a quantum computer. This is the approach being adopted by U.K.-based Quantum Resistant Ledger, initiated by Dr. Peter Waterland, a medical professional by day and champion of quantum resistant cryptocurrency by night. Another U.K.-based company, Ubiquicoin, has also announced its goal to “become the first blockchain resistant to quantum computing cyberattacks.”

The third method is quantum networks, which use hardware technology called quantum key distribution to send information from one point to another by encoding data on individual particles. Any attempted hack automatically severs the connection. A Russian group is employing this technology for blockchain while a similar concept, dubbed qBitcoin, was proposed at Osaka University in Japan.

Quantum-proofing blockchain is crucial for both the American public and private sector. Yet the U.S. currently lags behind Canada, Australia, South Korea, and Switzerland, all of which have companies with commercially available quantum cybersecurity products. Meanwhile, China continues its global dominance in quantum networks.

The threat posed by quantum computing to blockchain is serious. But following the three-step plan to develop and implement quantum keys, quantum resistant algorithms, and quantum networks can save blockchain from the dustbin of history and keep cryptocurrencies like Bitcoin from going bankrupt in the quantum age.